The branch of dentistry dealing with teeth irregularities and their corrections, such as by means of braces, is known as Orthodontics. The primary purpose of orthodontic treatment is to alter the position and reorient an individual's teeth so as to modify or improve their function. Teeth may also be reoriented mainly for cosmetic reasons.
In orthodontic treatment, as currently practiced, it is often necessary to affix various orthodontic appliances to the surfaces of a patient's teeth. The location of the orthodontic appliance on the tooth as well as its orientation is a critical factor in determining the direction of movement of the teeth during the treatment, and accurate placement may ensure that the teeth are aligned with a single bracket bonding treatment. Conversely, less accurate placement of orthodontic appliances may require repeated treatments, including repeated bonding and wire bending procedures until the final alignment is achieved.
Once the position of the orthodontic appliances has been decided upon, it is thus critical that a good bond is established between the orthodontic appliances and the teeth at that position. Orthodontic appliances affixed to teeth surfaces serve to support wires and tensioning springs to exert moments of force acting to move the teeth subjected to these forces to a degree and in a direction causing the teeth to assume a desired posture in the dental arch.
In current orthodontic practice, the orthodontist decides on a general scheme of placing the orthodontic appliances on the teeth and then attaches each of them to the surface of a tooth, in an exact location and orientation previously decided. Preparatory to an orthodontic treatment, the orthodontist typically prepares a plaster model of the teeth of the treated individual and on the basis of such model, and the general scheme of placement of the orthodontic appliances can be decided.
A typical treatment plan includes, among other factors, the desired position of each of the force-inducing orthodontic implements on the teeth. The placement of the orthodontic appliances on the teeth determines the outcome of the above-mentioned movements, e.g. the degree and direction of the teeth movements. Any deviation from the planned position of the orthodontic appliances affects the outcome of the treatment. Thus, during the process of placing the orthodontic appliances on the teeth, much effort is made to ensure the accurate positioning of the orthodontic appliances in accordance with their desired position as determined by the treatment plan, and to ensure that the orthodontic appliances are properly bonded to the teeth at these positions.
The orthodontic appliances are typically placed on the buccal surface of the teeth, though at times, it is desired both from a treatment perspective as well as for reasons of external appearance of the individual, to place the orthodontic appliances on the lingual surface of the teeth.
One form of positioning brackets is known as indirect bonding, and is traditionally based on forming a tray of a thermoplastic material, or any other suitable material, over a physical model of the teeth on which the brackets have been positioned using a relatively weak adhesive, for example as described in U.S. Pat. No. 3,738,005. The brackets may be positioned onto the model in any one of a number of ways, for example as disclosed in U.S. Pat. No. 4,812,118. The tray thus comprises a negative impression of the teeth model, which is very close-fitting with respect thereto, and also has the brackets embedded in position in the tray in their correct positions with respect to the model. The tray can then be removed from the model, taking with it the brackets in the correct relative positions with respect to the negative impression. The tray is then transferred to the intraoral cavity of the patient, and when properly fitted over the appropriate arch, presents the brackets in ostensibly the correct positions vis-à-vis the teeth. It is then attempted to bond the brackets simultaneously onto the teeth, and the tray may then be removed, leaving the brackets in place.
This method is commonly practiced, and can be used for both buccal and lingual brackets. Most of the preparatory work is done by a technician rather than the dentist, and the technique results in a shorter installation time than when the brackets are installed manually one at a time, but the technician needs to have a supply of brackets readily available. This method also requires all the teeth to be dry and pre-etched, before bonding begins.
Some patent publications of general background interest include: U.S. Pat. Nos. 5,971,754; 4,360,341; 6,123,544; 4,501,554, US 2005/0244790; US 2004/0253562; US 2004/0229185.